feat: add --download-path option (#536)

* feat: add --download-path option

Adds a `--download-path` flag (and `AGENT_BROWSER_DOWNLOAD_PATH` env / `downloadPath` config key) to set a default download directory for browser downloads.

Without this, Playwright stores downloads in a temp directory that is deleted when the browser closes. The new option passes through to Playwright's `downloadsPath` on `launch()` and `launchPersistentContext()`.

Fixes #507

* improvements

* fixes

* fixes

src/types.ts

@@ -32,6 +32,7 @@ export interface LaunchCommand extends BaseCommand {
   ignoreHTTPSErrors?: boolean;
   allowFileAccess?: boolean; // Enable file:// URL access and cross-origin file requests
   colorScheme?: 'light' | 'dark' | 'no-preference'; // Persistent color scheme override
+  downloadPath?: string; // Directory for browser downloads (Playwright's downloadsPath)
   // Auto-load state file for session persistence
   autoStateFilePath?: string;
 }